1. Field of the Invention
This invention relates generally to the dehydration of alcohols to form unsaturated organic compounds, and more specifically to an improved dehydration process employing novel silylated dehydration catalysts.
2. Description of the Prior Art
The liquid phase dehydration of aralkanols to aralkenes by the process of U.S. Pat. No. 3,526,674 achieves high aralkanol conversions to aralkene employing a temperature above about 200.degree. C. "High surface area" solids are preferred as dehydration catalysts: these solids are defined as having a surface area in excess of about 15 sq. meters per gram as determined by the Brunauer-Emmett-Teller method. See Smith, Chemical Engineering Kinetics, pages 216-221 (New York, 1956). Activated carbon, natural clays, molecular sieves, silica-aluminas and activated aluminas are exemplified in U.S. Pat. No. 3,526,674 as suitable high surface area solids. Others, such as titania are also useful.
The use of such dehydration catalysts in finely divided form as a suspension of a solids in a liquid phase requires the use of a certain amount of agitation to maintain the suspension. As the power consumed in the operation of agitation devices, in addition to the volume of the liquid (and hence the size of the process equipment) needed to form a slurry, will increase with any increase in the amount of dehydration catalyst employed, any increase of the activity of the dehydration catalyst would permit a decrease in the amount of catalyst used to effect a given conversion and would greatly lower overall processing costs.
Silylated catalysts for the epoxidation of olefins are known from British Pat. No. 1,339,309 to Wulff, in which a solid inorganic oxygen compound of silica in combination with an oxide or hydroxide of titanium, molybdenum, vanadium, zirconium or boron is treated with a silylating agent prior to epoxidation. U.S. Pat. No. 3,980,586 to Mitchell relates to modified refractory metal oxide solids which are sequentially silylated, calcined and steamed to provide compositions which are stated to be suitable catalysts in hydrocracking, alkylation, dealkylation, transalkylation, isomerization, hydrogenation, dehydrogenation, dehydrohalogenation and dehydrocyclization. However, the catalysts and process of British Pat. No. 1,339,309 and U.S. Pat. No. 3,980,586 are not readily adaptable for use in an alcohol dehydration process.